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<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <button>按钮</button>
    <script>
        var button = document.querySelector('button');

        // function fn() {
        //     console.log(11);
        //     button.removeEventListener('click', fn)
        // }
        // button.addEventListener('click', fn)
        button.onclick = function() {
            console.log(11);
        }
        button.onclick = null
    </script>
</body>

</html>